Electronics > Projects, Designs, and Technical Stuff

Continuity tester circuit

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2N3055:

--- Quote from: OM222O on August 30, 2019, 01:00:48 pm ---I know you can throw a micro controller at pretty much anything these days and call it quits, but it's a really bad practice that makes you lazy and prevents creativity / problem solving skills. all in all, it's bad engineering  ;)

--- End quote ---

Thanks for reminding me that most of the  time people doesn't want help, but confirmation how they know best...

It 's not bad or lazy engineering, it's different engineering and works very well. I didn't recommend to use whole Arduino board, or RPi.
ELM-chan's schematic has less and cheaper parts, has variable pitch to indicate resistance, is protected from voltages in circuit, and uses very little current. Your definition of good engineering is different form mine..
All you needed to say that you want (for whatever reason) fully analog solution.
No need to insult people for using microcontroller.
Especially if it is a very good solution.

Have a good one.

fourfathom:

--- Quote from: OM222O on August 30, 2019, 01:00:48 pm ---
--- Quote from: fourfathom on August 30, 2019, 12:43:01 am ---When the microcontroller costs $0.57 (qty 1) perhaps it isn't overkill?  Welcome to the new world!

--- End quote ---

I know you can throw a micro controller at pretty much anything these days and call it quits, but it's a really bad practice that makes you lazy and prevents creativity / problem solving skills. all in all, it's bad engineering  ;)

--- End quote ---

This is thread drift, but you started it!  Anyway, I'm here for the philosophy as much as the tech discussion:

Building creativity and problem-solving skills is very important, but do that on your own time if necessary.  If the problem you are tasked with can be solved simply and obviously and well and cheaply, then that's how you should solve it.

Now that I'm retired, I get to define my own problems.  Sometimes it just "get the job done".  Other times it's "I wonder if I can make this hair-brained scheme actually work?"  I'm a true believer in elegance as an engineering principle, but that's not the only principle to be considered.  And to a large extent elegance is in the eye of the beholder.  I consider that 50-cent micro design to be elegant.  A three-transistor design with a resistor bridge might also be elegant.  Neither one would be "bad engineering", and which was more suitable would depend on the customer requirements.

kripton2035:
here I collected lots of schematics around the web about continuity testers. enjoy.
http://kripton2035.free.fr/continuity-repos.html

IconicPCB:
Krypton,
Thank You.

Quite a few years ago i came across the 1995 EDN article and built the buzzer.

At the time I was interested in locating copper shorts on PCBs.

This buzzer is a Phenomenal Performer. It will zero in on the copper short along a track to within tens of millimeters.

OM222O:
As a really barebones version I tried it with an MCP6002 and it seems to be fairly reliable, so I bought a couple of LM393As just because the local RS had them available and I wanted to make the prototypes quickly  :-DD

Now I'm not sure if the device already contains ESD protection diodes or if I should add some (I even searched for "diode" in the datasheet and it didn't find anything). The output is open collector which is nice, since if I want to interface it with an MCU for automated testing, I can just use the pullups on the MCU and have an active low signal, regardless of the MCU voltage. In an AnalogDevices app note I read adding extra diodes can throw off the accuracy (i.e: input offset voltage) by quite a lot (almost 25mV!) so I want to avoid that if the device is already protected (although absolute accuracy is not that important, since in the final application, I will use an analog mux rather than building the same circuit 32 times for automated probing! analog muxes have quite a large tolerance on the contact resistance).

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